The Model Churn Tax: Why Assistant Portability Beats Model Loyalty for Agencies

Frontier assistants now ship new model tiers every few weeks, so the durable agency advantage is not picking the strongest model but owning a portable prompt, data, and evaluation layer that survives each swap. Agencies that treat assistants as interchangeable backends can reprice delivery against whichever model is cheapest per task that month; agencies that hard-wire one vendor absorb every price change and every regression as an unrecoverable margin hit.